The prevalence of vitamin D deficiency increases as kidney function declines. As a result, many hemodialysis patients often have low levels of vitamin D. Recent evidence has shown that vitamin D supplementation may improve many aspects of poor health such as heart disease and inflammatory markers. The objectives of this study are to determine how supplementing dialysis patients with ergocalciferol increases vitamin D levels, how long vitamin D levels can be maintained after a 6 month treatment course, and to examine the effect of ergocalciferol on biomarkers of inflammation and vascular health.